Diamine compounds for use in electrophotographic photoconductors

ABSTRACT

An electrophotographic photoconductor includes an electroconductive support and a photoconductive layer formed thereon containing a diamine compound represented by formula (I): ##STR1## wherein R 1 , R 2 , and R 3  each is independently a substituted or unsubstituted alkyl group or aryl group; R 4  is hydrogen, an alkyl group or an alkoxyl group; n is an integer of 1 to 3; and ##STR2## is a substituted or unsubstituted bivalent arylene group or a bivalent heterocyclic group. This diamine compound is useful as a photoconductive material for electrophotographic photoconductors.

This is a Division of application Ser. No. 08/326,224 filed on Oct. 20,1994, now U.S. Pat. No. 5,489,495.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrophotographic photoconductor,and more particularly an electrophotographic photoconductor comprisingan electroconductive support and a photoconductive layer comprising andiamine compound as an organic photoconductive material, which is formedon the electroconductive support. The present invention also relates todiamine compounds for use as organic photoconductive materials for theelectrophotographic photoconductor.

2. Discussion of Background

Conventionally, inorganic materials such as selenium, cadmium sulfideand zinc oxide are used as a photoconductive material of anelectrophotographic photoconductor in an electrophotographic process.The electrophotographic process is an image formation processes, throughwhich the surface of a photoconductor is charged uniformly in the darkto a predetermined polarity, for instance, by corona charge. Theuniformly charged photoconductor is exposed to a light image toselectively dissipate the electrical charges of the exposed areas, sothat a latent electrostatic image is formed on the photoconductor. Thethus formed latent electrostatic image is developed by a developercomprising a coloring agent such as a dye and a pigment, and a binderagent such as a polymeric material, to a visible image.

Fundamental characteristics required for the photoconductor for in suchan electrophotographic process are: (1) chargeability to an appropriatepotential in the dark, (2) minimum dissipation of electrical charge inthe dark, and (3) rapid dissipation of electrical charge when exposed tolight.

However, while the above-mentioned inorganic materials have manyadvantages, they have several shortcomings from the viewpoint ofpractical use.

For instance, a selenium photoconductor, which is widely used atpresent, satisfies the above-mentioned requirements (1) to (3)completely, but it has the shortcomings that its manufacturingconditions are difficult and, accordingly, its production cost is high.In addition, it is difficult to work it into the form of a belt due toits poor flexibility, and it is so vulnerable to heat and mechanicalshocks that it must be handled with the utmost care.

A cadmium sulfide photoconductor and a zinc oxide photoconductor can beeasily obtained by coating a dispersion of cadmium sulfide particles andzinc oxide particles in a binder resin on a support. However, they arepoor in mechanical properties, such as surface smoothness, hardness,tensile strength and wear resistance. Therefore, they cannot be used inthe repeated operation, as they are.

To solve the problems of the inorganic materials, variouselectrophotographic photoconductors employing organic materials areproposed recently and some are still put to practical use. For example,there are known a photoconductor comprising poly-N-vinylcarbazole and2,4,7-trinitrofluorene-9-on, as disclosed in U.S. Pat. No. 3,484,237; aphotoconductor prepared by sensitizing poly-N-vinylcarbazole with apigment of pyrylium salt, as described in Japanese Patent Publication48-25658; a photoconductor comprising as the main component an organicpigment, as described in Japanese Laid-Open Patent Application 47-37543;a photoconductor comprising as the main component an eutectic crystalcomplex of a dye and a resin, as described in Japanese Laid-Open PatentApplication 47-10735; a photoconductor prepared by sensitizing atriphenylamine compound with a sensitizer pigment, as described in U.S.Pat. No. 3,180,730; a photoconductor comprising an amine derivative as acharge transporting material, as described in Japanese Laid-Open PatentApplication 57-195254; a photoconductor comprising poly-N-vinylcarbazoleand an amine derivative as charge transporting materials, as describedin Japanese Laid-Open Patent Application 58-1155; and a photoconductorcomprising a polyfunctional tertiary amine compound, in particularbenzidine compound, as a photoconductive material, as described in U.S.Pat. No. 3,265,496, Japanese Patent Publication 39-11546 and JapaneseLaid-Open Patent Application 53-27033.

These electrophotographic photoconductors have their own excellentcharacteristics and considered to be valuable for practical use. Withvarious requirements of the electrophotographic photoconductor inelectrophotography taken into consideration, however, theabove-mentioned conventional electrophotographic photoconductors cannotmeet all the requirements for use in electrophotography.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention to provide anelectrophotographic photoconductor free from the conventionalshortcomings, which can completely satisfy all the requirements in theelectrophotographic process, including excellent flexibility.

A second object of the present invention is to provide a photoconductivematerial for use in the above-mentioned electrophotographicphotoconductor.

The first object of the present invention can be achieved by anelectrophotographic photoconductor comprising an electroconductivesupport and a photoconductive layer formed thereon comprising as aneffective component at least a diamine compound of formula (I): ##STR3##wherein R¹, R², and R³ each is independently a substituted orunsubstituted alkyl group or aryl group; R⁴ is hydrogen, an alkyl groupor an alkoxyl group; n is an integer of 1 to 3; and ##STR4## is asubstituted or unsubstituted bivalent arylene group or a bivalentheterocyclic group.

The second object of the present invention can be achieved by a diaminecompound of the above formula (I).

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view of a first example of anelectrophotographic photoconductor according to the present invention;

FIG. 2 as a schematic cross-sectional view of a second example of anelectrophotographic photoconductor according to the present invention;

FIG. 3 as a schematic cross-sectional view of a third example of anelectrophotographic photoconductor according to the present invention;

FIG. 4 as a schematic cross-sectional view of a fourth example of anelectrophotographic photoconductor according to the present invention;

FIG. 5 is a schematic cross-sectional view of a fifth example of anelectrophotographic photoconductor according to the present invention;and

FIG. 6 as an infrared spectrum of a diamine compound,N-(1-pyrenyl)-N,N',N'-tris(4-methylphenyl)-o-tolidine, according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The diamine compound for use in the electrophotographic photoconductoraccording to the present invention is a diamine compound with thefollowing formula (I): ##STR5## wherein R¹, R², and R³ each isindependently a substituted or unsubstituted alkyl group or aryl group;R⁴ is hydrogen, an alkyl group or an alkoxyl group; n is an integer of 1to 3; and ##STR6## is a substituted or unsubstituted bivalent arylenegroup or a bivalent heterocyclic group.

The above compound is a novel compound and can be synthesized by thecombination of (a) an N-alkyl substitution reaction or N-arylsubstitution reaction of an amino compound corresponding to the diaminecompound and (b) an N-pyrenyl substitution reaction. For the alkylation,arylation and pyrenyl condensation, corresponding halides are generallyemployed, and for diaryl condensation, Ullmann reaction is generallyemployed. In the Ullmann reaction, a solvent, for instance,N-dimethylformamide, nitrobenzene, dimethylsulfoxide, anddichlorobenzene can be employed. As a basic compound serving as an agentfor removing HZ (wherein Z is a halogen atom) produced in the course ofthe Ullmann reaction, for instance, potassium carbonate, sodiumcarbonate, sodium hydrogencarbonate can be employed. The reactiontemperature is usually in a range of 160° to 250° C.

When the reactivities of employed components for the Ullmann reactionare low, the reaction may be carried out at elevated temperatures in anautoclave or the like. Catalysts such as copper powder, copper oxide andhalogenated copper are usually used for promoting the reaction.

In the formula (I) of the diamine compound, when R¹, R² and/or R³ is anaryl group, specific examples of such an aryl group include a non-fusedhydrocarbon group such as phenyl group, biphenylyl group, andterphenylyl group, and a fused polycyclic hydrocarbon group.

It is preferable that the fused polycyclic hydrocarbon group be suchthat the number of carbon atoms which form rings be 18 or less. Specificexamples of such a fused polycyclic hydrocarbon group include pentalenylgroup, indenyl group, naphthyl group, azulenyl group, heptalenyl group,biphenylenyl group, as-indacenyl group, fluorenyl group, s-indacenylgroup, acenaphthylenyl group, pleiadenyl group, acenaphthenyl group,phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group,acephenanthrenyl group, aceanthrenyl group, triphenylenyl group, pyrenylgroup, chrysenyl group, and naphthacenyl group.

Furthermore, when ##STR7## in formula (I) is an arylene group, specificexamples of such an arylene group include a bivalent group of amonocyclic hydrocarbon compound such as benzene, diphenyl ether,polyethylene glycol diphenyl ether, diphenylthio ether, anddiphenylsulfone; a bivalent group of a non-fused polycyclic hydrocarboncompound such as biphenyl, polyphenyl, diphenyl alkane, diphenyl alkene,diphenyl alkyne, triphenyl methane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenyl alkane, and polyphenyl alkene; bivalent groups offused polycyclic hydrocarbons previously mentioned as specific examplesof R¹ ; and bivalent groups of hydrocarbon ring assemblies such as9,9-diphenylfluorenone.

When ##STR8## in formula (I) is a bivalent heterocyclic group, specificexamples of such a bivalent heterocyclic group include bivalent groupsof carbazole, dibenzofuran, dibenzothiophene, oxadiazole, andthiadiazole.

When R¹, R² and/or R³ is an aryl group, and ##STR9## is a bivalent groupof an arylene group or heterocyclic group, the aryl group or thebivalent group may have any of the following substituents:

(1) A halogen atom, cyano group, and nitro group.

(2) An alkyl group, preferably a straight chain or branched alkyl grouphaving 1 to 12 carbon atom, more preferably having 1 to 8 carbon atoms,furthermore preferably having 1 to 4 carbon atoms. These alkyl groupsmay have a substituent such as a fluorine atom, a hydroxyl group, acyano group, an alkoxyl group having 1 to 4 carbon atoms, or a phenylgroup which may have a substituent such as a halogen atom, an alkylgroup having 1 to 4 carbon atoms, or an alkoxyl group having 1 to 4carbon atoms. Specific examples of such an alkyl group are methyl group,ethyl group, n-propyl group, i-propyl group, t-butyl group, s-butylgroup, n-butyl group, i-butyl group, trifluoromethyl group,2-hydroxyethyl group, 2-cyanoethyl group, 2-ethoxyethyl group,2-methoxyethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzylgroup, 4-methoxy-benzyl group, and 4-phenylbenzyl group.

(3) An alkoxyl group (--OR⁵) in which R⁵ is the same alkyl group asabove defined in (2). Specific examples of such an alkoxyl group aremethoxy group, ethoxy group, n-propoxy group, i-propoxy group, t-butoxygroup, n-butoxy group, s-butoxy group, i-butoxy group, 2-hydroxyethoxygroup, 2-cyano-ethoxy group, benzyloxy group, 4-methylbenzyloxy group,and trifluoromethoxy group.

(4) An aryloxy group. Examples of the aryl group in the aryloxy groupare phenyl group and naphthyl group. The aryloxy group may have asubstituent such as an alkoxyl group having 1 to 4 carbon atoms, analkyl group having 1 to 4 carbon atoms, or a halogen atom. Specificexamples of the aryloxy group are phenoxy group, 1-naphthyloxy group,2-naphthyloxy group, 4-methylphenoxy group, 4-methoxyphenoxy group,4-chlorophenoxy group, and 6-methyl-2-naphthyloxy group.

(5) An alkylmercapto group or an arylmercapto group. Specific examplesof the alkylmercapto or arylmercapto group are methylthio group,ethylthio group, phenylthio group, and p-methylphenylthio group.##STR10## in which R⁶ and R⁷ each is hydrogen, the alkyl group asdefined in (2), or an aryl group. Specific examples of the aryl groupare phenyl group, biphenylyl group, and naphthyl group, which may have asubstituent such as an alkoxyl group having 1 to 4 carbon atoms, analkyl group having 1 to 4 carbon atoms, or a halogen atom. R⁶ and R⁷ incombination may form a ring, or may form a ring in combination with acarbon atom in the aryl group. Specific examples of this amino or aminoderivative group are amino group, diethyl amino group,N-methyl-N-phenylamino group, N,N-diphenylamino group,N,N-di(p-tolyl)amino group, benzylamino group, piperidino group,morpholino group, and julolidyl group.

(7) An alkylenedioxy or alkylenedithio group such as methylenedioxygroup and methylenedithio group.

When any of R¹, R², R³ and R⁴ is an alkyl group, specific examples ofthe alkyl group may be the same as provided in (2) above.

Specific examples of the diamine compound represented by formula (I) areshown in the following TABLE 1:

                                      TABLE 1                                     __________________________________________________________________________     ##STR11##                                                                        ##STR12##                                                                                    ##STR13##                                                                              ##STR14##                                                                              ##STR15##                                                                              ##STR16##                                                                         ##STR17##                   __________________________________________________________________________     1                                                                                ##STR18##                                                                                    ##STR19##                                                                              ##STR20##                                                                              ##STR21##                                                                             H   1-                            2 "                                                                                             ##STR22##                                                                              ##STR23##                                                                              ##STR24##                                                                             H   1-                            3 "                                                                                             ##STR25##                                                                              ##STR26##                                                                              ##STR27##                                                                             H   1-                            4 "                                                                                             ##STR28##                                                                              ##STR29##                                                                              ##STR30##                                                                             H   1-                            5                                                                                ##STR31##                                                                                    ##STR32##                                                                              ##STR33##                                                                              ##STR34##                                                                             H   1-                            6 "                                                                                             ##STR35##                                                                              ##STR36##                                                                              ##STR37##                                                                             H   1-                            7 "                                                                                             ##STR38##                                                                              ##STR39##                                                                              ##STR40##                                                                             H   1-                            8 "                                                                                             ##STR41##                                                                              ##STR42##                                                                              ##STR43##                                                                             H   1-                            9 "                                                                                             ##STR44##                                                                              ##STR45##                                                                              ##STR46##                                                                             H   1-                           10 "                                                                                             ##STR47##                                                                              ##STR48##                                                                              ##STR49##                                                                             H   1-                           11 "                                                                                             ##STR50##                                                                              ##STR51##                                                                              ##STR52##                                                                             H   1-                           12 "                                                                                             ##STR53##                                                                              ##STR54##                                                                              ##STR55##                                                                             H   1-                           13                                                                                ##STR56##     C.sub.2 H.sub.5                                                                        C.sub.2 H.sub.5                                                                        C.sub.2 H.sub.5                                                                        H   1-                           14 "                                                                                             ##STR57##                                                                              ##STR58##                                                                              ##STR59##                                                                             7-t-Bu                                                                            1-                           15 "                                                                                             ##STR60##                                                                              ##STR61##                                                                              ##STR62##                                                                             H   4-                           16 "                                                                                             ##STR63##                                                                              ##STR64##                                                                              ##STR65##                                                                             H   1-                           17 "                                                                                             ##STR66##                                                                              ##STR67##                                                                              ##STR68##                                                                             H   1-                           18 "                                                                                             ##STR69##                                                                              ##STR70##                                                                              ##STR71##                                                                             H   1-                           19 "                                                                                             ##STR72##                                                                              ##STR73##                                                                              ##STR74##                                                                             H   1-                           20 "              C.sub.2 H.sub.5                                                                        C.sub.4 H.sub.9                                                                        C.sub.4 H.sub.9                                                                        H   1-                           21 "              C.sub.2 H.sub.5                                                                        C.sub.2 H.sub.5                                                                         ##STR75##                                                                             H   1-                           22 "                                                                                             ##STR76##                                                                              ##STR77##                                                                              ##STR78##                                                                             H   1-                           23 "                                                                                             ##STR79##                                                                              ##STR80##                                                                              ##STR81##                                                                             H   1-                           24 "              pyrenyl  pyrenyl  pyrenyl  H   1-                                             (1-)     (1-)     (1-)                                      25                                                                                ##STR82##                                                                                    ##STR83##                                                                              ##STR84##                                                                              ##STR85##                                                                             H   1-                           26 "                                                                                             ##STR86##                                                                              ##STR87##                                                                              ##STR88##                                                                             H   1-                           27                                                                                ##STR89##                                                                                    ##STR90##                                                                              ##STR91##                                                                              ##STR92##                                                                             H   1-                           28 "                                                                                             ##STR93##                                                                              ##STR94##                                                                              ##STR95##                                                                             H   1-                           29 "                                                                                             ##STR96##                                                                              ##STR97##                                                                              ##STR98##                                                                             H   1-                           30 "                                                                                             ##STR99##                                                                              ##STR100##                                                                             ##STR101##                                                                            H   1-                           31 "              pyrenyl (1-)                                                                            ##STR102##                                                                             ##STR103##                                                                            H   1-                           32 "                                                                                             ##STR104##                                                                             ##STR105##                                                                             ##STR106##                                                                            H   1-                           33 "              C.sub.2 H.sub.5                                                                        C.sub.2 H.sub.5                                                                         ##STR107##                                                                            H   1-                           34                                                                                ##STR108##                                                                                   ##STR109##                                                                             ##STR110##                                                                             ##STR111##                                                                            H   1-                           35                                                                                ##STR112##                                                                                   ##STR113##                                                                             ##STR114##                                                                             ##STR115##                                                                            H   1-                           36                                                                                ##STR116##                                                                                   ##STR117##                                                                             ##STR118##                                                                             ##STR119##                                                                            H   1-                           37 "                                                                                             ##STR120##                                                                             ##STR121##                                                                             ##STR122##                                                                            H   1-                           38                                                                                ##STR123##                                                                                   ##STR124##                                                                             ##STR125##                                                                             ##STR126##                                                                            H   1-                           39                                                                                ##STR127##                                                                                   ##STR128##                                                                             ##STR129##                                                                             ##STR130##                                                                            H   1-                           40                                                                                ##STR131##                                                                                   ##STR132##                                                                             ##STR133##                                                                             ##STR134##                                                                            H   1-                           41                                                                                ##STR135##                                                                                   ##STR136##                                                                             ##STR137##                                                                             ##STR138##                                                                            H   1-                           42                                                                                ##STR139##                                                                                   ##STR140##                                                                             ##STR141##                                                                             ##STR142##                                                                            H   1-                           43 "                                                                                             ##STR143##                                                                             ##STR144##                                                                             ##STR145##                                                                            H   1-                           44 "                                                                                             ##STR146##                                                                             ##STR147##                                                                             ##STR148##                                                                            H   1-                           45                                                                                ##STR149##                                                                                   ##STR150##                                                                             ##STR151##                                                                             ##STR152##                                                                            H   1-                           46                                                                                ##STR153##                                                                                   ##STR154##                                                                             ##STR155##                                                                             ##STR156##                                                                            H   1-                           47                                                                                ##STR157##                                                                                   ##STR158##                                                                             ##STR159##                                                                             ##STR160##                                                                            H   1-                           48                                                                                ##STR161##                                                                                   ##STR162##                                                                             ##STR163##                                                                             ##STR164##                                                                            H   1-                           49                                                                                ##STR165##                                                                                   ##STR166##                                                                             ##STR167##                                                                             ##STR168##                                                                            H   1-                           50                                                                                ##STR169##                                                                                   ##STR170##                                                                             ##STR171##                                                                             ##STR172##                                                                            H   1-                           51                                                                                ##STR173##                                                                                   ##STR174##                                                                             ##STR175##                                                                             ##STR176##                                                                            H   1-                           52                                                                                ##STR177##                                                                                   ##STR178##                                                                             ##STR179##                                                                             ##STR180##                                                                            H   1-                           53                                                                                ##STR181##                                                                                   ##STR182##                                                                             ##STR183##                                                                             ##STR184##                                                                            H   1-                           54 "                                                                                             ##STR185##                                                                             ##STR186##                                                                             ##STR187##                                                                            H   1-                           55 "                                                                                             ##STR188##                                                                             ##STR189##                                                                             ##STR190##                                                                            H   1-                           56                                                                                ##STR191##                                                                                   ##STR192##                                                                             ##STR193##                                                                             ##STR194##                                                                            H   1-                           57 "                                                                                             ##STR195##                                                                             ##STR196##                                                                             ##STR197##                                                                            H   1-                           58 "                                                                                             ##STR198##                                                                             ##STR199##                                                                             ##STR200##                                                                            H   1-                           59 "                                                                                             ##STR201##                                                                             ##STR202##                                                                             ##STR203##                                                                            H   1-                           60                                                                                ##STR204##                                                                                   ##STR205##                                                                             ##STR206##                                                                             ##STR207##                                                                            H   1-                           61                                                                                ##STR208##                                                                                   ##STR209##                                                                             ##STR210##                                                                             ##STR211##                                                                            H   1-                           __________________________________________________________________________     Note) SPPR*: Substitution Position of Pyrene Ring                        

Of the diamine compounds covered by the above-mentioned formula (I), adiamine compound of the following formula (Ia) may also be particularlyuseful as a photoconductive material for use in the electrophotographicphotoconductor according to the present invention: ##STR212## whereinR¹, R² and R³ each is independently a substituted or unsubstituted alkylgroup or aryl group; R⁴ is hydrogen, a halogen atom, methoxy group ormethyl group; R⁵ is hydrogen or methyl group; R⁶ is hydrogen, an alkylgroup or an alkoxyl group; and n is an integer of 1 to 3.

The diamine compound of formula (Ia) can be synthesized, for example, bythe following steps:

(1) The following diamine compound of formula (II) to N-acetylation issubjected to N-acetylation to obtain an N-acetylated compound of thediamine compound of formula (II): ##STR213## wherein R⁴ is hydrogen,chlorine, methoxy group or methyl group; and R⁵ is hydrogen or methylgroup.

(2) The thus obtained N-acetylated compound is then subjected to anN,N',N'-three-substitution reaction by use of a halide of the followingformula (III) to obtain a condensation product:

    R.sup.1 Z.sup.1, R.sup.2 Z.sup.1 or R.sup.3 Z.sup.1        (III)

wherein R¹, R² and R³ each is independently a substituted orunsubstituted alkyl group or aryl group; and Z¹ is a chlorine atom, abromine atom or an iodine atom.

(3) The thus obtained condensation product is hydrolyzed.

(4) The hydrolyzed condensation product is condensed with a pyrenylhalide of formula (IV) by the Ullmann condensation reaction, whereby theabove-mentioned diamine compound of formula (Ia) can be synthesized:##STR214## wherein R⁶ is hydrogen, an alkyl group, or an alkoxyl group;n is an integer of 1 to 3; and Z² is bromine or iodine.

Alternatively, a 4-iodo-4'-nitro-1,1'-biphenyl compound of formula (V)is condensed with an amine compound of formula (VI) to prepare acondensation product: ##STR215## wherein R⁴ is hydrogen, chlorine,methoxy group or methyl group; and R⁵ is hydrogen or methyl group.##STR216## wherein R¹ is a substituted or unsubstituted alkyl group oraryl group; R⁶ is hydrogen, an alkyl group or an alkoxyl group; and n isan integer of 1 to 3.

The thus obtained condensation product is reduced and condensed with thepreviously mentioned halide of formula (III) by the Ullmann condensationreaction, whereby the diamine compound of formula (Ia) can be obtained.

When each of R¹, R², and R³ of the previously mentioned formula (III) isan alkyl group, the diamine compound of formula (II) can also be used asan acid removing agent for removing HX wherein X is a halogen in thecourse of the reaction. Alternatively, the N,N,N'-three-substitutionreaction is carried out by use of an organic amine, sodiumhydrogencarbonate, potassium hydrogencarbonate, sodium carbonate orpotassium carbonate, each of which has a stronger basicity than thediamine compound of formula (II), as the acid removing agent in thepresence of a polar solvent such as pyridine, acetone, THF, methanol, orethanol, or without solvent.

Examples of the thus obtained diamine compound of formula (Ia) accordingto the present invention are as follows:

In formula (Ia), specific examples of the alkyl group represented by R¹,R², or R³ include methyl group, ethyl group, propyl group, butyl groupand benzyl group. Specific examples of the aryl group represented by R¹,R², or R³ include phenyl group, biphenylyl group, terphenylyl group,naphthyl group, and anthryl group. These groups may have any of thefollowing substituents: an alkyl group such as methyl group, ethylgroup, propyl group, and butyl group; an alkoxyl group such as methoxygroup, ethoxy group, propoxy group, and butoxy group; an alkylmercaptogroup such as methylthio group and ethylthio group; an aryloxy groupsuch as phenoxy group and naphthyloxy group; and a halogen.

When any of R¹, R², or R³ has a plurality of substituents, suchsubstituents may be the same or different.

Specific examples of the alkyl group represented by R⁶ are methyl group,ethyl group and butyl group; and specific examples of the alkoxyl grouprepresented by R⁶ are methoxy group and ethoxy group.

Specific examples of the diamine compound of formula (II) serving as astarting material for the synthesis of the diamine compound of formula(Ia) are benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine,3,3'-dichlorobenzidine, and 3,3',5,5'-tetramethylbenzidine.

The diamine compounds according to the present invention, which areremarkably effective as photoconductive materials for use inelectrophotographic photoconductors, can be optically or chemicallysensitized with a sensitizer such as a dye or Lewis acid. In addition,the diamine compounds effectively function as a charge transportingmaterial in a function-separated type electrophotographic photoconductorwhere an organic or inorganic pigment serves as a charge generatingmaterial.

Specific examples of a sensitizing dye for use in the present inventionare triarylmethane dyes such as Brilliant Green, Victoria Blue B, MethylViolet, Crystal Violet and Acid Violet 6B; xanthene dyes such asRhodamine B, Rhodamine 6G, Rhodamine G Extra, Eosin S, Erythrosin, RoseBengale and Fluoresceine; thiazine dyes such as Methylene Blue; cyaninedyes such as cyanin; pyrylium dyes such as2,6-diphenyl-4-(N,N-dimethylaminophenyl)thiapyrylium perchlorate andbenzopyrylium salts (described in Japanese Patent Publication 48-25658);2,4,7-trinitro-9-fluorenone; and 2,4-dinitro-9-fluorenone. Thesesensitizing dyes can be used alone or in combination.

Examples of the above-mentioned organic pigments include azo pigmentssuch as C.I. Pigment Blue 25 (C.I. 21180), C.I. Pigment Red 41 (C.I.21200), and C.I. Pigment Red 3 (C.I. 45210); phthalocyanine pigmentssuch as C.I. Pigment Blue 16 (C.I. 74100); indigo pigments such as C.I.Vat Brown 5 (C.I. 73410) and C.I. Vat Dye (C.I. 73030); and perylenepigments such as Algol Scarlet B and Indanthrene Scarlet R.

Examples of the inorganic pigments are selenium, selenium--tellurium,cadmium sulfide, cadmium sulfide--selenium and α-silicone.

In the photoconductors according to the present invention, at least onediamine compound of formula (I) is contained in the photoconductivelayers 2, 2a, 2b, 2c and 2d. The diamine compound can be employed indifferent ways, for example, as shown in FIGS. 1 through 5.

In the photoconductor as shown in FIG. 1, a photoconductive layer 2 isformed on an electroconductive support 1, which photoconductive layer 2comprises a diamine compound of the present invention, a sensitizing dyeand a binder agent (binder resin). In this photoconductor, the diaminecompound works as a photoconductive material, through which chargecarriers which are necessary for the light decay of the photoconductorare generated and transported. However, the diamine compound itselfscarcely absorbs light in the visible light range and, therefore, it isnecessary to add a sensitizing dye which absorbs light in the visiblelight range in order to form latent electrostatic images by use ofvisible light.

Referring to FIG. 2, there is shown an enlarged cross-sectional view ofanother embodiment of an electrophotographic photoconductor according tothe present invention. In the figure, reference numeral 1 indicates anelectroconductive support. On the electroconductive support 1, there isformed a photoconductive layer 2a comprising a charge generatingmaterial 3 dispersed in a charge transporting medium 4 comprising adiamine compound and a binder agent. In this embodiment, the diaminecompound and the binder agent (or a mixture of the binder agent and aplasticizer) in combination constitute the charge transporting medium 4.The charge generating material 3, which is, for example, an inorganic ororganic pigment, generates charge carriers. The charge transportingmedium 4 accepts the charge carriers generated by the charge generatingmaterial 3 and transports those charge carriers.

In this electrophotographic photoconductor, it is basically necessarythat the light-absorption wavelength regions of the charge generatingmaterial 3 and the polyether compound not overlap in the visible lightrange. This is because, in order that the charge generating material 3produce charge carriers efficiently, it is necessary that light passthrough the charge transporting medium 4 and reach the surface of thecharge generating material 3. Since the diamine compounds of thepreviously described general formula (I) do not substantially absorblight in the visible range, they can work effectively as chargetransporting materials in combination with the charge generatingmaterial 3 which absorbs the light in the visible region and generatescharge carriers.

Referring to FIG. 3, there is shown an enlarged cross-sectional view ofa further embodiment of an electrophotographic photoconductor accordingto the present invention. In the figure, there is formed on anelectroconductive support 1 a two-layered photoconductive layer 2bcomprising a charge generation layer 5 containing the charge generatingmaterial 3, and a charge transport layer 4 containing a diamine compoundof the previously described formula (I).

In this photoconductor, light which has passed through the chargetransport layer 4 reaches the charge generation layer 5, and chargecarriers are generated within the charge generation layer 5. The chargecarriers which are necessary for the light decay for latentelectrostatic image formation are generated by the charge generatingmaterial 3, accepted and transported by the charge transport layer 4. Inthe charge transport layer 4, the polyether compound mainly works fortransporting charge carriers. The generation and transportation of thecharge carriers are performed by the same mechanism as that in thephotoconductor shown in FIG. 2.

Referring to FIG. 4, there is shown still another embodiment of anelectrophotographic photoconductor according to the present invention.In the figure, the overlaying order of the charge generation layer 5 andthe charge transport layer 4 is reversed in view of theelectrophotographic photoconductor as shown in FIG. 3. The mechanism ofthe generation and transportation of charge carriers is substantiallythe same as that of the photoconductor shown in FIG. 3.

In the above photoconductor, a protective layer 6 may be formed on thecharge generation layer 5 as shown in FIG. 5 for protecting the chargegeneration layer 5.

When the electrophotographic photoconductor according to the presentinvention as shown in FIG. 1 is prepared, at least one diamine compoundof the previously described formula (I) is dispersed in a binder resinsolution, and a sensitizing dye is then added to the mixture, so that aphotoconductive layer coating liquid is prepared. The thus preparedphotoconductive layer coating liquid is coated on an electroconductivesupport 1 and dried, so that a photoconductive layer 2 is formed on theelectroconductive support 1.

It is preferable that the thickness of the photoconductive layer 2 be inthe range of 3 to 50 μm, more preferably in the range of 5 to 20 μm. Itis preferable that the amount of the diamine compound contained in thephotoconductive layer 2 be in the range or 30 to 70 wt. %, morepreferably about 50 wt. %.

It is preferable that the amount of the sensitizing dye contained in thephotoconductive layer 2 be in the range of 0.1 to 5 wt. %, morepreferably in the range of 0.5 to 3 wt. %.

The electrophotographic photoconductor shown in FIG. 2 can be obtainedby dispersing finely-divided particles of the charge generating material3 in the solution in which at least one diamine compound for use in thepresent invention and the binder agent are dissolved, coating theabove-prepared dispersion on the electroconductive support 1 and thendrying the same to form the photoconductive layer 2a.

It is preferable that the thickness of the photoconductive layer 2a bein the range of 3 to 50 μm, more preferably in the range of 5 to 20 μm.It is preferable that the amount of the diamine compound contained inthe photoconductive layer 2a be in the range or 10 to 95 wt. %, morepreferably in the range of 30 to 90 wt. %.

It is preferable that the amount of the charge generating material 3contained in the photoconductive layer 2a be in the range of 0.1 to 50wt. %, more preferably in the range of 1 to 20 wt. %.

Specific examples of the charge generating material 3 for use in thepresent invention are as follows: inorganic pigments such as selenium,selenium--tellurium, cadmium sulfide, cadmium sulfide--selenium andα-silicone; and organic pigments, such as C.I. Pigment Blue 25 (C.I.21180), C.I. Pigment Red 41 (C.I. 21200), C.I. Acid Red 52 (C.I. 45100),and C.I. Basic Red 3 (C.I. 45210); an azo pigment having a carbazoleskeleton (Japanese Laid-Open Patent Application 53-95033), an azopigment having a distyryl benzene skeleton (Japanese Laid-Open PatentApplication 53-133445), an azo pigment having a triphenylamine skeleton(Japanese Laid-Open Patent Application 53-132347), an azo pigment havinga dibenzothiophene skeleton (Japanese Laid-Open Patent Application54-21728), an azo pigment having an oxadiazole skeleton (JapaneseLaid-Open Patent Application 54-12742), an azo pigment having afluorenone skeleton (Japanese Laid-Open Patent Application 54-22834), anazo pigment having a bisstilbene skeleton (Japanese Laid-Open PatentApplication 54-17733), an azo pigment having a distyryl oxadiazoleskeleton (Japanese Laid-Open Patent Application 54-2129), and an azopigment having a distyryl carbazole skeleton (Japanese Laid-Open PatentApplication 54-14967); a phthalocyanine pigment such as C.I. PigmentBlue 16 (C.I. 74100); indigo pigments such as C.I. Vat Brown 5 (C.I.73410) and C.I. Vat Dye (C.I. 73030); and perylene pigments such asAlgol Scarlet B and Indanthrene Scarlet R (made by Bayer Co., Ltd.).These charge generating materials may be used alone or in combination.

The electrophotographic photoconductor shown in FIG. 3 can be obtainedas follows:

The charge generating material is vacuum-deposited on theelectroconductive support 1, or the dispersion in which finely-dividedparticles of the charge generating material 3 is dispersed in anappropriate solvent, together with the binder agent when necessary, iscoated on the electroconductive support 1 and dried, so that the chargegeneration layer 5 is formed. When necessary, the charge generationlayer 5 is subjected to surface treatment by buffing and adjustment ofthe thickness thereof. On the thus formed charge generation layer 5, acoating solution in which at least one polyether compound and the binderagent are dissolved is coated and dried, so that the charge transportlayer 4 is formed. In the charge generation layer 5, the same chargegenerating material as employed in the above-mentioned photoconductivelayer 2a can be used.

The thickness of the charge generation layer 5 is 5 μm or less, morepreferably 2 μm or less. It is preferable that the thickness of thecharge transport layer 4 be in the range of 3 to 50 μm, more preferablyin the range of 5 to 20 μm. When the charge generation layer 5 isobtained by coating the dispersion in which finely-divided particles ofthe charge generating material 3 is dispersed in an appropriate solventtogether with the binder agent, it is preferable that the amount offinely-divided particles of the charge generating material 3 containedin the charge generation layer 5 be in the range of 10 to 95 wt. %, morepreferably in the range of about 50 to 90 wt. %. It is preferable thatthe amount of the polyether compound contained in the charge transportlayer 4 be in the range of 10 to 95 wt. %, more preferably in the rangeof 30 to 90 wt. %.

The electrophotographic photoconductor shown in FIG. 4 can be obtainedas follows:

A coating solution in which the diamine compound and the binder agentare dissolved is coated on the electroconductive support 1 and dried toform the charge transport layer 4. On the thus formed charge transportlayer 4, a dispersion prepared by dispersing finely-divided particles ofthe charge generating material 3 in the solvent, in which the binderagent is dissolved when necessary, is coated by spray coating and driedto form the charge generation layer 5 on the charge transport layer 4.The amount ratio of components contained in the charge generation layerand charge transport layer is the same as previously described in FIG.3.

The electrophotographic photoconductor shown in FIG. 5 can be obtainedby forming a protective layer 6 on the charge generation layer 5 asobtained in FIG. 4 by spray-coating of an appropriate resin solution. Asa resin employed in the protective layer 6, any of binder agents to bedescribed later can be used.

Specific examples of the electroconductive support 1 for theelectrophotographic photoconductor according to the present inventioninclude a metallic plate or foil made of aluminum, a plastic film onwhich a metal such as aluminum is deposited, and a sheet of paper whichhas been treated so as to be electroconductive.

Specific examples of the binder agent for use in the present inventionare condensation resins such as polyamide, polyurethane, polyester,epoxy resin, polyketone and polycarbonate; and vinyl copolymers such aspolyvinylketone, polystyrene, poly-N-vinylcarbazole and polyacrylamide.Any insulating and adhesive resins can be employed.

Some plasticizers may be added to the abovementioned binder agent, whennecessary. Examples of the plasticizer for use in the present inventionare halogenated paraffin, polybiphenyl chloride, dimethylnaphthalene anddibutyl phthalate.

Furthermore, in the electrophotographic photoconductors according to thepresent invention, an adhesive layer or barrier layer may be interposedbetween the electroconductive support and the photoconductive layer whennecessary. Examples of the material for use in the adhesive layer orbarrier layer are polyamide, nitrocellulose and aluminum oxide. It ispreferable that the thickness of the adhesive layer or barrier layer be1 μm or less.

When copying is performed by use of the photoconductors according to thepresent invention, the surface of the photoconductor is chargeduniformly in the dark to a predetermined polarity. The uniformly chargedphotoconductor is exposed to a light image so that a latentelectrostatic image is formed on the photoconductor. The thus formedlatent electrostatic image is developed by a developer to a visibleimage, and when necessary, the developed image can be transferred to asheet of paper. The electrophotographic photoconductors according to thepresent invention have the advantages in that the photosensitivity ishigh and the flexibility is improved.

Other features of this invention will become apparent in the course ofthe following description of exemplary embodiments, which are given forillustration of the invention and are not intended to be limitingthereof.

PREPARATION EXAMPLE 1-1 [Synthesis of Diamine Compound No. 27 in TABLE1]

42.5 g (0.2 mol) of o-tolidine was dissolved in 200 ml of methanol. Tothis solution, 20.4 g (0.2 mol) of acetic anhydride was added dropwiseover a period of 2 hours. After the dropwise addition of the aceticanhydride, the reaction mixture was poured over 300 g of ice, so thatseparated crystals were filtered off.

The thus obtained crystals were dispersed in an aqueous solution ofhydrochloric acid composed of 100 ml of hydrochloric acid and 1000 ml ofwater. This mixture was stirred at room temperature for 1 hour and wasthen filtered to obtain a filtrate. To the filtrate was added potassiumhydroxide to make the filtrate highly basic. Crystals separated from thefiltrate were filtered off, whereby N-acetyl-o-tolidine (m.p. 207°-209°C.) was obtained in a yield of 24.0 g (47%).

The infrared spectrum absorption of νc=o measured by a commerciallyavailable infrared spectrophotometer IR-700 (made by Nippon Bunko KogyoCo., Ltd.) by using a KBr tablet was 1651 cm⁻¹.

To 50 ml of nitrobenzene, 7.63 g (30 mmol) of the thus obtainedN-acetyl-o-tolidine, 21.8 g (100 mmol) of p-iodotoluene, 0.63 g (10mmol) of copper powder, and 14.7 g (150 mmol) of anhydrous potassiumcarbonate were added. The mixture was stirred at 200° C. for 10 hours.

After this stirring with application of heat, this reaction mixture waspoured into an aqueous solution of 5.6 g (100 mmol) of 96% potassiumhydroxide in a mixture of 50 ml of isoamyl alcohol and 20 ml of water,and hydrolyzed at 120° C. for 8 hours.

The reaction mixture was steam distilled to remove the isoamyl alcoholand nitrobenzene therefrom and was extracted with 200 ml of toluene.

With insoluble components removed from the toluene layer by filtration,the toluene layer was washed water, dried, and concentrated. Crystalswere obtained from the residue. The thus obtained crystals werecolumn-chromatographed for purification on silica gel and eluted with amixed solvent of toluene and n-hexane (1:2), wherebyN,N,N'-tris(4-methylphenyl)-o-tolidine (m.p. 141.0°-143.0° C.) wasobtained in a yield of 10.9 g (74%).

3.93 g (10 mmol) of the thus obtainedN,N,N'-tris(4-methylphenyl)-o-tolidine, 4.10 g (12.5 mmol) of1-iodopyrene, 0.19 g (3 mmol) of copper powder, and 3.92 g (40 mmol) ofanhydrous potassium carbonate were added to 50 ml of nitrobenzene. Thisreaction mixture was stirred at 200° C. for 7 hours.

After the completion of this stirring with the application of heat, thereaction mixture was extracted with 100 ml of toluene, and the toluenelayer was concentrated, whereby a yellow oil was obtained as a reactionproduct.

The thus obtained yellow oil was column-chromatographed for purificationon silica gel and eluted with a mixed solvent of toluene and n-hexane(1:2), whereby N-(1-pyrenyl)-N,N',N'-tris(4-methylphenyl)-o-tolidine(m.p. 232.0°-233.5° C.) was obtained in a yield of 3.11 g (39%).

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       90.05        6.44   3.89                                          Calculated  89.70        6.20   4.10                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-Pyrenyl)-N,N',N'-tris(4-methylphenyl)-o-tolidine of C₅₁ H₄₂ N₂.

FIG. 6 shows an infrared spectrum ofN-(1-pyrenyl)-N,N',N'-tris(4-methylphenyl)-o-tolidine, taken by use of aKBr tablet.

PREPARATION EXAMPLE 1-2 [Synthesis of Diamine Compound No. 28 in TABLE1]

7.63 g (30 mmol) of N-acetyl-o-tolidine synthesized in PreparationExample 1-1, 21.8 g (100 mmol) of m-iodotoluene, 0.63 g (10 mmol) ofcopper powder, and 14.7 g (150 mmol) of anhydrous potassium carbonatewere added to 50 ml of nitrobenzene. The mixture was stirred at 200° C.for 10 hours.

After this stirring with application of heat, this reaction mixture waspoured into an aqueous solution of 5.6 g (100 mmol) of 96% potassiumhydroxide in a mixture of 50 ml of isoamyl alcohol and 20 ml of water,and hydrolyzed at 120° C. for 12 hours.

The reaction mixture was steam distilled to remove the isoamyl alcoholand nitrobenzene therefrom and was extracted with 200 ml of toluene.

With insoluble components removed from the toluene layer by filtration,the toluene layer was washed water, dried, and concentrated. Crystalswere obtained from the residue. The thus obtained crystals werecolumn-chromatographed for purification on silica gel and eluted with amixed solvent of toluene and n-hexane (1:2), wherebyN,N,N'-tris(3-methylphenyl)-o-tolidine was obtained in a yield of 12.5 g(85%).

3.93 (10 mmol) of the thus obtainedN,N,N'-tris(4-methylphenyl)-o-tolidine, 4.10 g (12.5 mmol) of1-iodopyrene, 0.19 g (3 mmol) of copper powder, and 3.92 g (40 mmol) ofanhydrous potassium carbonate were added to 50 ml of nitrobenzene. Thisreaction mixture was stirred at 200° C. for 7 hours.

After the completion of this stirring with the application of heat, thereaction mixture was extracted with 100 ml of toluene, and the toluenelayer was concentrated, whereby a yellow oil was obtained as a reactionproduct.

The thus obtained yellow oil was column-chromatographed for purificationon silica gel and eluted with a mixed solvent of toluene and n-hexane(1:2), whereby N-(1-pyrenyl)-N,N',N'-tris(3-methylphenyl)-o-tolidine(with a melting initiation point of 130.5° C.) was obtained in a yieldof 2.3 g (34%).

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       89.80        6.50   3.80                                          Calculated  89.70        6.20   4.10                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-pyrenyl)-N,N',N'-tris (3-methylphenyl)-o-tolidine of C₅₁ H₄₂ N₂.

PREPARATION EXAMPLE 1-3 [Synthesis of Diamine Compound No. 29 in TABLE1]

7.63 g (30 mmol) of N-acetyl-o-tolidine synthesized in PreparationExample 1-1, 23.6 g (100 mmol) of p-iodoanisole, 0.63 g (10 mmol) ofcopper powder, and 14.7 g (150 mmol) of anhydrous potassium carbonatewere added to 50 ml of nitrobenzene. The mixture was stirred at 200° C.for 10 hours.

After this stirring with application of heat, this reaction mixture waspoured into an aqueous solution of 5.6 g (100 mmol) of 96% potassiumhydroxide in a mixture of 50 ml of isoamyl alcohol and 20 ml of water,and hydrolyzed at 120° C. for 8 hours.

The reaction mixture was steam distilled to remove the isoamyl alcoholand nitrobenzene therefrom and was extracted with 200 ml of toluene.

With insoluble components removed from the toluene layer by filtration,the toluene layer was washed water, dried, and concentrated. Crystalswere obtained from the residue. The thus obtained crystals werecolumn-chromatographed for purification on silica gel and eluted with amixed solvent of toluene and n-hexane (1:2), wherebyN,N,N'-tris(4-methoxyphenyl)-o-tolidine (m.p. 96.0°-98.5° C.) wasobtained in a yield of 8.14 g (54%).

5.30 g (10 mmol) of the thus obtainedN,N,N'-tris(4-methoxyphenyl)-o-tolidine, 4.10 g (12.5 mmol) of1-iodopyrene, 0.19 g (3 mmol) of copper powder, and 3.92 g (40 mmol) ofanhydrous potassium carbonate were added to 50 ml of nitrobenzene. Thisreaction mixture was stirred at 200° C. for 12 hours.

After the completion of this stirring with the application of heat, thereaction mixture was extracted with 100 ml of toluene, and the toluenelayer was concentrated, whereby a yellow oil was obtained as a reactionproduct.

The thus obtained yellow oil was column-chromatographed for purificationon silica gel and eluted with a mixed solvent of toluene and n-hexane(1:5), whereby N-(1-pyrenyl)-N,N',N'-tris(4-methoxyphenyl)-o-tolidine(m.p. 175.0°-177.5° C.) was obtained in a yield of 2.6 g (36%).

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       84.07        5.88   3.30                                          Calculated  83.81        5.79   3.80                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-pyrenyl)-N,N',N'-tris (4-methoxyphenyl)-o-tolidine of C₅₁ H₄₂ N₂O₃.

PREPARATION EXAMPLE 1-4 [Synthesis of Diamine Compound No. 30 in TABLE1]

7.63 g (30 mmol) of N-acetyl-o-tolidine synthesized in PreparationExample 1-1, 23.6 g (100 mmol) of m-iodoanisole, 0.63 g (10 mmol) ofcopper powder, and 14.7 g (150 mmol) of anhydrous potassium carbonatewere added to 50 ml of nitrobenzene. The mixture was stirred at 200° C.for 10 hours.

After this stirring with application of heat, this reaction mixture waspoured into an aqueous solution of 5.6 g (100 mmol) of 96% potassiumhydroxide in a mixture of 50 ml of isoamyl alcohol and 20 ml of water,and hydrolyzed at 120° C. for 8 hours.

The reaction mixture was steam distilled to remove the isoamyl alcoholand nitrobenzene therefrom and was extracted with 200 ml of toluene.

With insoluble components removed from the toluene layer by filtration,the toluene layer was washed water, dried, and concentrated. Crystalswere obtained from the residue. The thus obtained crystals werecolumn-chromatographed for purification on silica gel and eluted with amixed solvent of toluene and n-hexane (1:3), wherebyN,N,N'-tris(3-methoxyphenyl)-o-tolidine was obtained in a yield of 11.5g (79%).

5.30 g (10 mmol) of the thus obtainedN,N,N'-tris(3-methoxyphenyl)-o-tolidine, 4.10 g (12.5 mmol) of1-iodopyrene, 0.19 g (3 mmol) of copper powder, and 3.92 g (40 mmol) ofanhydrous potassium carbonate were added to 50 ml of nitrobenzene. Thisreaction mixture was stirred at 200° C. for 10 hours.

After the completion of this stirring with the application of heat, thereaction mixture was extracted with 100 ml of toluene, and the toluenelayer was concentrated, whereby a yellow oil was obtained as a reactionproduct.

The thus obtained yellow oil was column-chromatographed for purificationon silica gel and eluted with a mixed solvent of toluene and n-hexane(1:5), whereby N-(1-pyrenyl)-N,N',N'-tris(3-methoxyphenyl)-o-tolidine(m.p. 308.0°-310.0° C.) was obtained in a yield of 4.5 g (61%).

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       83.46        5.61   4.18                                          Calculated  83.81        5.79   3.80                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-pyrenyl)-N,N',N'-tris(3-methoxyphenyl)-o-tolidine of C₅₁ H₄₂ N₂ O₃.

PREPARATION EXAMPLE 1-5 [Synthesis of Diamine Compound No. 6 in TABLE 1]

5.0 g (16 mmol) of N-(m-tolyl)-1-aminopyrene, 5.3 g (16 mmol) of4-nitro-4'-iodobiphenyl, 1.03 g (16 mmol) of copper powder, and 6.63 g(48 mmol) of anhydrous potassium carbonate were added to 50 ml ofnitrobenzene. The mixture was stirred at 200° C. for 10 hours.

After this stirring with application of heat, this reaction mixture wasextracted with 100 ml of toluene. The toluene layer was concentrated,whereby red crystals were obtained from the residue.

The thus obtained red crystals were column-chromatographed forpurification on silica gel and eluted with a mixed solvent of tolueneand n-hexane (1:2), whereby4'-nitro-N-(m-tolyl)-N-(1-pyrenyl)-4-biphenylamine was obtained in ayield of 5.66 g (54%).

5.04 g (10 mmol) of the thus obtained4'-nitro-N-(m-tolyl)-N-(1-pyrenyl)-4-biphenylylamine was dissolved in150 ml of tetrahydrofuran, and 2 g of 5% palladium carbon (with awater-content of 51 wt. %) was added thereto in a hydrogenationapparatus. The nitro group of the4'-nitro-N-(m-tolyl)-N-(1-pyrenyl)-4-biphenylylamine was reduced at roomtemperature by the hydrogenation apparatus.

After the completion of the reduction reaction, the palladium carbon wasremoved from the reaction mixture by filtration, and the terahydrofuranwas distilled, wherebyN-(m-tolyl)-N-(1-pyrenyl)-[1,1'-biphenyl]-4,4'-diamine was obtained inthe form of crystals.

The thus obtainedN-(m-tolyl)-N-(1-pyrenyl)-[1,1'-biphenyl]-4,4'-diamine, 4.8 g (22 mmol)of m-iodotoluene, 0.3 g (5 mmol) of copper powder, 4.2 g (30 mmol) ofanhydrous potassium carbonate were added to 50 ml of nitrobenzene. Thisreaction mixture was stirred at 190° C. for 19 hours.

After the completion of this stirring with the application of heat, thereaction mixture was extracted with 100 ml of toluene, and the toluenelayer was concentrated, whereby a red oil was obtained as a reactionproduct.

The thus obtained red oil was column-chromatographed for purification onsilica gel and eluted with a mixed solvent of toluene and n-hexane(1:3), whereby N-(1-pyrenyl)-N,N',N'-tris(3-methylphenyl)benzidine(Diamine Compound No. 6) (with a melting-initiation point of 130° C.)was obtained in a yield of 2.0 g (31%).

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       89.83        5.93   4.06                                          Calculated  89.87        5.85   4.28                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-pyrenyl)-N,N',N'-tris (3-methylphenyl) benzidine of C₄₉ H₃₈ N₂.

PREPARATION EXAMPLE 1-6 [Synthesis of Diamine Compound No. 7 in TABLE 1]

2.71 g (5.2 mmol) of4'-nitro-N-(4-methoxyphenyl)-N-(1-pyrenyl)-4-biphenylylamine synthesizedin a similar manner to that in Preparation Example 1-5 was dissolved in150 ml of tetrahydrofuran, and 2 g of 5% palladium carbon (with awater-content of 51 wt. %) was added thereto in a hydrogenationapparatus. The nitro group of the4'-nitro-N-(4-methoxyphenyl)-N-(1-pyrenyl)-4-biphenylylamine was reducedat room temperature by the hydrogenation apparatus.

After the completion of the reduction reaction, the palladium carbon wasremoved from the reaction mixture by filtration, and the terahydrofuranwas distilled, wherebyN-(4-methoxyphenyl)-N-(1-pyrenyl)-[1,1'-biphenyl]-4,4'-diamine wasobtained in the form of crystals.

The thus obtainedN-(4-methoxyphenyl)-N-(1-pyrenyl)-[1,1'-biphenyl]-4,4'-diamine, 2.7 g(11 mmol) of p-iodoanisole, 0.3 g (5 mmol) of copper powder, 2.2 g (16mmol) of anhydrous potassium carbonate were added to 50 ml ofnitrobenzene. This reaction mixture was stirred at 190° C. for 18 hours.

After the completion of this stirring with the application of heat, thereaction mixture was extracted with 100 ml of toluene, and the toluenelayer was concentrated, whereby a red oil was obtained as a reactionproduct.

The thus obtained red oil was column-chromatographed for purification onsilica gel and eluted with a mixed solvent of dioxane and n-hexane(1:5), whereby N-(1-pyrenyl)-N,N',N'-tris(4-methoxyphenyl)benzidine(m.p. 211.0° to 213.0° C.) was obtained in a yield of 1.2 g (33%).

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       84.07        5.53   3.72                                          Calculated  83.73        5.45   3.99                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-pyrenyl)-N,N',N'-tris(4-methoxyphenyl)benzidine of C₄₉ H₃₈ N₂ O₃.

PREPARATION EXAMPLE 1-7 [Synthesis of Diamine Compound No. 60 in TABLE1]

By subjecting 4'-iodo-N-(p-tolyl)-N-(1-pyrenyl)-4-biphenlyamine and3-methylbiphenylylamine to the same Ullmann reaction as in PreparationExample 1-6, wherebyN-(1-Pyrenyl)-N-(p-tolyl)-N'-phenyl-N'-(m-tolyl)benzidine (m.p.172.0°-173.0° C.) was obtained.

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       89.46        5.32   4.32                                          Calculated  89.96        5.66   4.37                                          ______________________________________                                    

The above calculation was based on the formula forN-(1-Pyrenyl)-N-(p-tolyl)-N'-phenyl-N'-(m-tolyl)benzidine of C₄₈ H₃₆ N₂.

PREPARATION EXAMPLE 1-8 [Synthesis of Diamine Compound No. 61 in TABLE1]

3,3',5,5'-tetramethylbenzidine was monoacetylated by a conventionalmethod, and the thus obtained monoacetylated compound and p-iodotolueneto the Ullmann reaction, wherebyN,N,N'-tris(4-methylphenyl)-N'-acetyl-3,3',5,5'-tetramethylbenzidine wasobtained.

The thus obtainedN,N,N'-tris(4-methylphenyl)-N'-acetyl-3,3',5,5'-tetramethylbenzidine washydrolyzed, and the hydrolyzed product and 1-iodo-pyrene were subjectedto the same Ullmann reaction as in Preparation Example 1-6, wherebyN,N,N'-tris(4-methylphenyl)-N'-(1-pyrenyl)-3,3',5,5'-tetramethylbenzidine(m.p. 198.0°-199.0° C.) was obtained.

The results of the elemental analysis of the thus obtained compound wereas follows:

    ______________________________________                                                  % C        % H    % N                                               ______________________________________                                        Found       89.14        6.74   3.96                                          Calculated  89.54        6.52   3.94                                          ______________________________________                                    

The above calculation was based on the formula forN,N,N'-tris(4-methylphenyl)-N'-(1-pyrenyl)-3,3',5,5'-tetramethylbenzidineof C₅₃ H₄₆ N₂.

EXAMPLE 2-1

76 parts by weight of Diane Blue (C.I. Pigment Blue 25, CI21180) servingas a charge generating material, 1260 parts by weight of a 2%tetrahydrofuran solution of a polyester resin (Trademark "Vylon 200"made by Toyobo Company, Ltd.) and 3700 parts by weight oftetrahydrofuran were dispersed and ground in a ball mill. The thusprepared dispersion was coated on an aluminum surface of analuminum-deposited polyester film by a doctor blade, and dried at roomtemperature, so that a charge generation layer with a thickness of about1 μm was formed on the aluminum-deposited polyester film.

2 parts by weight of diamine compound No. 6 in TABLE 1, 2 parts byweight of polycarbonate resin (Trademark "Panlite K-1300" made by TeijinLimited.) and 16 parts by weight of tetrahydrofuran were mixed to form asolution.

This solution was coated on the above formed charge generation layer bya doctor blade and then dried at 80° C. for 2 minutes and then at 120°C. for 5 minutes, so that a charge transport layer with a thickness ofabout 20 μm was formed on the charge generation layer. Thus atwo-layered type electrophotographic photoconductor No. 1 according tothe present invention was prepared.

EXAMPLES 2-2 to 2-23

The procedure for preparation of the two-layered typeelectrophotographic photoconductor No. 1 in Example 2-1 was repeatedexcept that Diane Blue serving as a charge generating material and thediamine compound No. 6 serving as a charge transporting materialemployed in Example 2-1 were replaced by the respective chargegenerating materials and charge transporting materials listed in thefollowing TABLE 2, whereby two-layered type electrophotographicphotoconductors No. 2 to No. 23 according to the present invention wereprepared.

    TABLE 2      -   Charge Transporting Material      Example No. Charge Generating Material (Diamine Derivative)      1     ##STR217##      Compound No. 6      2     ##STR218##      Compound No. 6      3     ##STR219##      Compound No. 6      4     ##STR220##      Compound No. 6      5     ##STR221##      Compound No. 6      6     ##STR222##      Compound No. 6      7 β     type Copper Phthalocyanine Compound No. 6      8     ##STR223##      Compound No. 7      9     ##STR224##      Compound No. 7     10 P-1 Compound No. 7      11 P-2 Compound No. 7      12 P-3 Compound No. 7      13 P-1      Compound No. 27              Charge Transporting Material      Example No. Charge Generating Material (Diamine Compound No.)      14 P-2 27      15 P-3 27      16 P-1 28      17 P-2 28      18 P-3 28      19 P-1 29      20 P-2 29      21 P-3 29      22 P-2 60      23 P-2 61

EXAMPLE 2-24

Selenium was vacuum-deposited on an aluminum plate with a thickness ofabout 300 μm, so that a charge generation layer with a thickness ofabout 1 μm was formed on the aluminum plate.

2 parts by weight of diamine compound No. 6 in TABLE 1, 3 parts byweight of polyester resin (Trademark "Polyester Adhesive 49000" made byDu Pont de Nemours, E.I. & Co.) and 45 parts by weight oftetrahydrofuran were mixed to form a solution. This solution was coatedon the above formed charge generation layer by a doctor blade, dried atroom temperature, and then dried under reduced pressure, so that acharge transport layer with a thickness of about 10 μm was formed on thecharge generation layer. Thus a two-layered type electrophotographicphotoconductor No. 24 according to the present invention was prepared.

EXAMPLE 2-25

The procedure for preparation of the two-layered electrophotographicphotoconductor No. 24 in Example 2-24 was repeated except that a chargegeneration layer with a thickness of about 0.6 μm was formed on the samealuminum plate as employed in Example 2-24 by deposition of thefollowing perylene pigment instead of selenium, so that a two-layeredelectrophotographic photoconductor No. 25 according to the presentinvention was prepared: ##STR225##

EXAMPLE 2-26

A mixture of 1 part by weight of the same Diane Blue as employed inExample 2-1 and 158 parts by weight of tetrahydrofuran was dispersed andground in a ball mill to form a dispersion. To the thus formeddispersion, 12 parts by weight of diamine compound No. 6 in TABLE 1 and18 parts by weight of polyester resin (Trademark "Polyester Adhesive49000" made by Du Pont de Nemours, E.I. & Co.) were added to form asolution.

This solution was coated on an aluminum-deposited polyester film by adoctor blade, and dried at 100° C. for 30 minutes, so that aphotoconductive layer with a thickness of about 16 μm was formed on theelectroconductive support. Thus, an electrophotographic photoconductorNo. 26 according to the present invention was prepared.

EXAMPLE 2-27

2 parts by weight of diamine compound No. 6 in TABLE 1, 2 parts byweight of polycarbonate resin (Trademark "Panlite K-1300" made by TeijinLimited.) and 16 parts by weight of tetrahydrofuran were mixed to form asolution.

This solution was coated on an aluminum surface of an aluminum-depositedpolyester film by a doctor blade and then dried at 80° C. for 2 minutesand then at 120° C. for 5 minutes, so that a charge transport layer witha thickness of about 20 μm was formed on the aluminum-depositedpolyester.

A mixture of 13.5 parts by weight of bisazo pigment (P-2), 5.4 parts byweight of polyvinyl butyral (Trademark "XYHL" made by Union CarbideJapan K. K.), 680 parts by weight of tetrahydrofuran and 1020 parts byweight of ethyl cellosolve was dispersed and ground in a ball mill. Tothis dispersion, 1700 parts by weight of additional ethyl cellosolve wasadded to form a solution. This solution was coated on the above formedcharge transport layer by spray coating and dried at 100° C. for 10minutes, so that a charge generation layer with a thickness of about 0.2μm was formed on the charge transport layer.

A methanol--n-butanol based solution of a polyamide resin (Trademark"CM-8000" made by Toray Silicone Co., Ltd.) was coated on the aboveformed charge generation layer by spray coating and dried at 120° C. for30 minutes, so that a protective layer having a thickness of about 0.5μm was formed on the charge generation layer. Thus, anelectrophotographic photoconductor No. 27 according to the presentinvention was prepared.

Each of the thus prepared electrophotographic photoconductors No. 1through No. 27 according to the present invention was charged negativelyor positively in the dark under application of -6 kV or +6 kV of coronacharge for 20 seconds, using a commercially available electrostaticcopying sheet testing apparatus ("Paper Analyzer Model SP-428" made byKawaguchi Electro Works Co., Ltd.). Then, each electrophotographicphotoconductor was allowed to stand in the dark for 20 seconds withoutapplying any charge thereto, and the surface potential Vpo (V) of thephotoconductor was measured. Each photoconductor was then illuminated bya tungsten lamp in such a manner that the illuminance on the illuminatedsurface of the photoconductor was 4.5 lux, and the exposure E_(1/2)(lux.sec) required to reduce the initial surface potential Vpo (V) to1/2 the initial surface potential Vpo (V) was measured. The results areshown in TABLE 3.

Each of the thus fabricated electrophotographic photoconductors Nos. 1to 27 according to the present invention was charged by use of acommercially available electrophotographic copying machine and exposedto a light image to form a corresponding latent electrostatic imagethereon. The thus formed latent electrostatic image formed on each ofthe photoconductors was developed with a dry developer to a visibletoner image. The thus formed toner image was then electrostaticallytransferred to a plain paper and fixed thereto. As a result, a cleartransferred toner image was obtained from each of the photoconductors.

When a liquid developer was employed instead of the dry developer, aclear transferred toner image was also obtained from each of theelectrophotographic photoconductors Nos. 1 to 27 of the presentinvention.

                  TABLE 3                                                         ______________________________________                                        Photoconductor -Vpo (V)  E.sub.l/2  (lux · sec)                      ______________________________________                                        No. 1          1023      1.90                                                 No. 2          993       1.70                                                 No. 3          1192      1.10                                                 No. 4          1221      1.87                                                 No. 5          1136      0.93                                                 No. 6          984       0.59                                                 No. 7          1210      1.32                                                 No. 8          917       1.58                                                 No. 9          735       1.20                                                 No. 10         821       0.83                                                 No. 11         597       0.59                                                 No. 12         485       0.30                                                 No. 13         1197      1.20                                                 No. 14         1128      1.07                                                 No. 15         947       0.88                                                 No. 16         1311      1.40                                                 No. 17         1256      1.20                                                 No. 18         1100      0.87                                                 No. 19         1103      1.03                                                 No. 20         1004      0.91                                                 No. 21         971       0.60                                                 No. 22         858       0.72                                                 No. 23         1085      0.95                                                 No. 24         1251      2.81                                                 No. 25         1393      3.72                                                 No. 26         -1095     1.70                                                 No. 27         -1240     0.98                                                 ______________________________________                                    

The electrophotographic photoconductors according to the presentinvention comprise a photoconductive layer comprising any of theabove-mentioned specific diamine compounds serving as an organicphotoconductive material, so that the resistance to heat and mechanicalshocks and the photoconductive properties can be significantly improved.Furthermore, the photoconductors according to the present invention canbe manufactured at low cost. Japanese Patent Application No. 5-285857filed on Oct. 20, 1993, Japanese Patent Application No. 5-296045 filedon Nov. 1, 1993, Japanese Patent Application No. 6-109088 filed on Apr.25, 1994, and Japanese Patent Application No. 6-109087 filed on Apr. 25,1994 are hereby incorporated by reference.

What is claimed is:
 1. A diamine compound represented by formula (I):##STR226## wherein R¹, R², and R³ each is independently a substituted orunsubstituted alkyl group or aryl group not including pyrenyl; R⁴ ishydrogen, an alkyl group or an alkoxyl group; n is an integer of 1 to 3;and ##STR227## is a substituted or unsubstituted bivalent arylene groupnot including phenylene, phenanthrenyl and 9,10-dihydrophenanthrenyl ora bivalent heterocyclic group.
 2. The diamine compound as claimed inclaim 1, wherein said alkyl group represented by R¹, R² and R³ is astraight chain or branched alkyl group having 1 to 12 carbon atoms. 3.The diamine compound as claimed in claim 1, wherein said aryl grouprepresented by R¹, R² and R³ is a non-fused hydrocarbon group.
 4. Thediamine compound as claimed in claim 1, wherein said aryl grouprepresented by R¹, R² and R³ is a fused polycyclic hydrocarbon group. 5.The diamine compound as claimed in claim 3, wherein said non-fusedhydrocarbon group is selected from the group consisting of phenyl group,biphenylyl group, and terphenylyl group.
 6. The diamine compound asclaimed in claim 4, wherein said fused polycyclic hydrocarbon group has18 or less carbon atoms which form rings therein.
 7. The diaminecompound as claimed in claim 6, wherein said fused polycyclichydrocarbon group is selected from the group consisting of pentalenylgroup, indenyl group, naphthyl group, azulenyl group, heptalenyl group,biphenylenyl group, as-indacenyl group, fluorenyl group, s-indacenylgroup, acenaphthylenyl group, pleiadenyl group, acenaphthenyl group,phenalenyl group, phenanthrenyl group, anthryl group, fluoranthenylgroup, acephenanthrenyl group, aceanthrenyl group, triphenylenyl group,chrysenyl group, and naphthacenyl group.
 8. The diamine compound asclaimed in claim 1, wherein said bivalent arylene group represented by##STR228## is a bivalent group of a substituted or unsubstitutedmonocyclic hydrocarbon compound.
 9. The diamine compound as claimed inclaim 8, wherein said monocyclic hydrocarbon compound is selected fromthe group consisting of diphenyl ether, polyethylene glycol diphenylether, diphenylthio ether, and diphenylsulfone.
 10. The diamine compoundas claimed in claim 1, wherein said bivalent arylene group representedby ##STR229## is a bivalent group of a non-fused polycyclic hydrocarboncompound.
 11. The diamine compound as claimed in claim 10, wherein saidbivalent group of a non-fused polycyclic hydrocarbon compound isselected from the group consisting of biphenyl, polyphenyl, diphenylalkane, diphenyl alkene, diphenyl alkyne, triphenyl methane,distyrylbenzene, 1,1-diphenylcyclo alkane, polyphenyl alkane, andpolyphenyl alkene.
 12. The diamine compound as claimed in claim 1,wherein said bivalent arylene group represented by ##STR230## is abivalent group of a fused polycyclic hydrocarbon compound.
 13. Thediamine compound as claimed in claim 12, wherein said fused polycyclichydrocarbon group has 18 or less carbon atoms which form rings therein.14. The diamine compound as claimed in claim 13, wherein said fusedpolycyclic hydrocarbon group is selected from the group consisting ofpentalenyl group, indenyl group, naphthyl group, azulenyl group,heptalenyl group, biphenylenyl group, as-indacenyl group, fluorenylgroup, s-indacenyl group, acenaphthylenyl group, pleiadenyl group,acenaphthenyl group, phenalenyl group, anthryl group, fluoranthenylgroup, acephenanthrenyl group, aceanthrenyl group, triphenylenyl group,pyrenyl group, chrysenyl group, and naphthacenyl group.
 15. The diaminecompound as claimed in claim 1, wherein said bivalent arylene grouprepresented by ##STR231## is a bivalent group of a hydrocarbon ringcompound.
 16. The diamine compound as claimed in claim 1, wherein saidbivalent heterocyclic group represented by ##STR232## is selected fromthe group consisting of bivalent groups of carbazole, dibenzofuran,dibenzo-thiophene, oxadiazole, and thiadiazole.
 17. A diamine compoundrepresented by formula (Ia): ##STR233## wherein R¹, R² and R³ each isindependently a substituted or unsubstituted alkyl group or aryl groupnot including pyrenyl; R⁴ is hydrogen, a halogen atom, methoxy group ormethyl group; R⁵ is hydrogen or methyl group; R⁶ is hydrogen, an alkylgroup or an alkoxyl group; and n is an integer of 1 to
 3. 18. Thediamine compound as claimed in claim 17, wherein said alkyl grouprepresented by R¹, R², or R³ is selected from the group consisting ofmethyl group, ethyl group, propyl group, butyl group and benzyl group.19. The diamine compound as claimed in claim 17, wherein said aryl grouprepresented by R¹, R², or R³ is selected from the group consisting ofphenyl group, biphenylyl group, terphenylyl group, naphthyl group, andanthryl group.
 20. The diamine compound as claimed in claim 17, whereinsaid alkyl group represented by R⁶ is selected from the group consistingof methyl group, ethyl group, and butyl group.
 21. The diamine compoundas claimed in claim 17, wherein said alkoxyl group represented by R⁶ isselected from the group methoxy group and ethoxy group.